1. Field
The inventive concept relates to a distributed antenna system (DAS), and more particularly, to a digital data transmission in a DAS.
2. Description of Related Art
When a distributed antenna system (DAS) interfaces with a base station through a digital interface standard, e.g., a common public radio interface (CPRI), an open baseband remote radiohead interface (OBSAI), an open radio interface (ORI), etc., if the DAS follows the interface standard of the base station as it is such that data received from the base station is transmitted from a head-end unit to a hub unit or remote unit in the DAS, the transmission capacity of data increases.
In the digital interface standard such as the CPRI, the OBSAI, or the ORI, a large amount of overhead is included in a transmitted data frame, and therefore, the transmission efficiency of data is low in actual payload transmission. Accordingly, there is required a method capable of efficiently transmitting signals transmitted according to the digital interface standard in a signal distributed system such as a DAS, which should transmit wideband signals.
In the digital interface standard such as the CPRI, the OBSAI, or the ORI, the sampling rate with respect to bandwidth (BW) is high. Also, stuffing bits are added to a payload portion corresponding to user data, and therefore, the number of bits in data transmission increases. In addition, the transmission efficiency with respect to the BW is lowered due to line coding such as 8B10B. In a DAS network, a plurality of digital interfaces should be employed so as to support a plurality of bands, providers, sectors, MIMO, etc., the transmission efficiency of data is lowered. Therefore, the transmission efficiency of data is low in the actual payload transmission, and hence the transmission capacity of data increases when the data is transmitted as it is.
Accordingly, there is required a transmission method capable of reducing an overhead of data in the digital interface standard by considering the transmission efficiency and transmission capacity of data in the DAS which should transmit wideband signals.